(a) Field of the Invention
The present invention relates to a compound oxide catalyst carrier which comprises silica-alumina or titania-alumina and is a useful catalyst or catalyst carrier for use in various processes, such as petroleum refining processes. Particularly, the present invention relates to a compound oxide catalyst carrier consisting of silica-alumina or titania-alumina or containing them as main components, which has a moderately uniform aluminum concentration distribution in solid particles, has a moderate acidity due to the absence of strong acid sites and is excellent particularly in attrition resistance and, therefore, is suitable for use as a catalyst carrier requiring attrition resistance and ability of inhibiting generation of coke or excessive cracking, such as a carrier of catalysts for production of useful middle distillate fractions by a suspension bed process hydrocracking of heavy oil.
The present invention further relates to a suitable method of producing the above-described compound oxide catalyst carrier.
The present invention further relates to a method of treating heavy oil for producing middle distillates efficiently, wherein heavy oil is hydrocracked by the above-described compound oxide catalyst carrier.
(b) Description of the Related Art
Hydrocracking of heavy oil, such as atmospheric residue, vacuum residue or petroleum derived from coal, shale or tar sands, using solid catalysts has been carried out for producing more useful middle distillates (MD). Such hydrocracking of heavy oil is generally conducted by a suspension bed process wherein catalyst particles are mixed with heavy oil and contact is made between the mixture and hydrogen, and the catalysts used have requirements for high attrition resistance as well as a requirement for good reaction results including a high yield of middle fraction of distillate and generation of little coke.
As the techniques for the hydrocracking of heavy oil by a suspension bed process, there have been proposed a method using FCC spent catalysts (specification of U.S. Pat. No. 4,082,648) and a method using direct desulfurization spent catalysts. For the above-described hydrocracking of heavy oil, however, the FCC spent catalysts are insufficient in catalytic activity, causing problems including a low yield of middle distillates (MD) and generation of much coke, and on the other hand, the direct desulfurization spent catalysts are not so poor in catalytic activity, but their mechanical strength is insufficient for saving them from attrition.
Other commonly proposed catalysts for suspension bed process hydrocracking of heavy oil than the above-described direct desulfurization spent catalysts are those comprising acidic compound oxide carriers, such as silica-alumina or titania-alumina, supporting metallic components, such as Ni-Mo, Co-Mo or Ni-W.
However, the conventional silica-alumina and titania-alumina, because of their extremely high acidity and insufficient mechanical strength including poor attrition resistance, are unsuitable either as the carriers of catalysts for suspension bed process hydrocracking of heavy oil or as other catalysts or catalyst carriers requiring high attrition resistance, so that their use is limited.